A method for optimizing the cruise flight aerodynamic conditions of aircraft with transonic airfoils and the relevant apparatus for performing this method are disclosed in German Patent Document 3,114,143 C2. The method disclosed therein serves to change the camber of the airfoil by ascertaining current or actual flight data during flight and determining a defined airfoil camber dependent on these data, whereby the actual flight data are the altitude, the flight speed, and the flight weight. The apparatus is formed by a flap system comprising a slat system as well as a trailing edge flap system of the airfoil, wherein the trailing edge flap system includes high lift flaps as well as spoilers, whereby the spoilers are respectively biased to lie tightly against the high lift flaps.
In a suitable aircraft, the known method extends the limits for the optimum cruising range or cruise flight condition, i.e. achieves a minimum fuel consumption or minimum flight time.
By the control measures provided within the context of the above method, the desired favorable aerodynamic configuration is maintained for a very much greater range of speed and angle of attack or lift than would be possible without such control measures. Furthermore, the trailing edge separation, the direct shock-induced separation, as well as the shock position at high Mach numbers can be controlled. The wing air flow is controlled simply by setting the optimum camber for the respective existing flight condition, whereby the optimum camber was determined in advance, based on measurements of the flow conditions that were determined as optimal for all possible flight conditions.
With the above method, the values determined in tests on a selected aircraft of a certain type are applied to all other aircraft of the same type. Since the wing air flow reacts very sensitively to changes in the determinative marginal conditions, it often happens that the camber determined by tests for a specific case does not result in the air flow that is actually optimal for this case. This can be caused when, among other things, differences exist between the test aircraft subjected to measurements and the actual aircraft equipped according to this conventional solution. In this context, the differences regard certain parameters that influence the air flow but that are not detectable or ascertainable in the above method. Such parameters are, for example, production-caused deviations of the aircraft geometry or changes in the surface roughness due to aging or contamination, whereby the contamination has an effect particularly in the leading edge areas of the airfoil and of the flaps. Therefore, the accuracy and thus also the effectiveness of the above method is substantially impaired by disturbances that are not readily detectable or ascertainable.
U.S. Pat. No. 4,741,503 discloses a system and a method for adjusting the camber of a wing profile for optimizing the flight performance. Therein, the horizontal speed of the aircraft is measured and the profile camber is varied until the measured speed has reached its maximum value. To carry out this method, a flight computer cooperates with a speed measuring sensor and actuators to activate camber flaps. The instantaneous horizontal speed is measured and a corresponding signal is sent to the flight computer, which in turn, based on a corresponding computer program, outputs signals for controlledly driving the actuators. In this way, the camber of the wing is set so that the horizontal speed achieves its maximum value. With this method, the optimum camber results as a mean value, whereby wing areas with a non-optimum camber continue to exist in addition to wing areas with an optimum camber.
A further system with a flight computer that acts on the flaps of an airfoil via actuators is disclosed in U.S. Pat. No. 5,135,186. In this system for controlling flutter phenomena, the periodic deflections of the airfoil are ascertained by sensors. The corresponding sensor signals are input into the flight computer, which in turn drives the respective actuators in such a way as to suppress the flutter movements. This patent provides no suggestion to reduce the air resistance.